All digital phased array using space/time cascaded processing

• US 20030206132A1
• Filed: 05/01/2002
• Published: 11/06/2003
• Est. Priority Date: 05/01/2002
• Status: Active Grant

• Current Assignee: North South Holdings Incorporated (Spherix Incorporated)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Martin, G. Patrick, Phelan, H. Richard, Nink, Richard J., Goldstein, Mark L.
• Granted Patent: US 6,738,018 B2
• Time in Patent Office: Days
• US Class Current: 342/157
• CPC Class Codes: G01S 3/74 Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14
• CPC Class Codes: G01S 7/2813 Means providing a modification of the radiation pattern for cancelling noise, clutter or interfering signals, e.g. side lobe suppression, side lobe blanking, null-steering arrays specially adapted to secondary radar systems G01S13/762; aerials or aerials systems H01Q21/29, H01Q25/00
• CPC Class Codes: H01Q 3/2605 Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence

Abstract

The invention concerns a method and apparatus for cascaded processing of signals in a phased array antenna system in which a plurality of antenna elements are configured as a plurality of sub-arrays. A weighting factor is applied to each of the antenna elements to form a plurality of sub-array beams, each pointed in a selected direction. For each sub-array, an output from each the antenna elements in the sub-array can be combined to produce a sub-array output signal. The sub-array output signals are selectively weighted and combined in a fully adaptive process. Subsequently, the system can estimate an angle-of-arrival direction for a signal-of-interest (“SOI”) and at least one signal-not-of-interest (“SNOI”). Based on this estimating step, the system calculates a new set of weighting factors for controlling one or more of the sub-array beams to improve the signal-to-noise plus interference ratio obtained for the SOI in the array output signal.

Claims

1. In a phased array antenna system having a plurality of antenna elements configured as a plurality of sub-arrays, a method for cascaded processing of signals to reduce interference from at least one undesired signal, comprising the steps of:

selectively applying a weighting factor to each of said antenna elements to form a plurality of sub-array beams, each pointed in a selected direction;

for each said sub-array, combining an output from each said antenna element in said sub-array to produce a sub-array output signal;

selectively weighting and combining said sub-array output signal received from at least one of said sub-arrays with a sub-array output signal from at least a second one of said sub-arrays in a fully adaptive process for producing an array output signal having a signal-to-noise plus interference ratio;

estimating an angle-of-arrival direction for a SOI and at least one SNOI;

responsive to said estimating step, calculating a new set of weighting factors for controlling at least one said sub-array beam to improve said signal-to-noise plus interference ratio obtained for said SOI in said array output signal; and

selectively controlling said weighting factors for said at least one sub-array beam in accordance with said calculating step.

2. The method according to claim 1 wherein said controlling step comprises adjusting said weighting factors for at least one of said sub-arrays for re-pointing said sub-array beam.

3. The method according to claim 1 wherein said controlling step comprises adjusting said weighting factors for at least one of said sub-arrays to produce a sub-array beam pattern comprising regions of relatively higher and lower gain to improve said signal-to-noise plus interference ratio.

4. The method according to claim 3 wherein said calculating step is further comprised of calculating a surrogate covariance matrix based solution for at least one of said sub-arrays.

5. The method according to claim 1 wherein said weighting factor is selected from the group consisting of exclusively amplitude, exclusively phase, time-delay and complex weights associated with each said antenna element.

6. The method according to claim 1 wherein said estimating step further comprises the step of estimating an incident power for at least one of said SOI and said at least one SNOI.

7. The method according to claim 1 wherein said selected direction in which at least one sub-array is initially pointed is a region of angular space expected to contain said SOI.

8. The method according to claim 1 wherein said estimating step further comprises a direction finding method based on at least one of:

blind source separation (BSS) techniques;

a priori knowledge;

direction information of signals learned during system operation.

9. The method according to claim 1 further comprising the steps of:

selectively applying at least one alternate weighting factor to each of said antenna elements in at least one of said sub-arrays to independently form at least one alternate sub-array beam using said antenna elements; and

combining an output from each said antenna element produced using said alternate weighting factor to produce at least one alternate sub-array output signal; and

selectively weighting and combining at least one of said sub-array output signals with said at least one alternate sub-array output signal in a fully adaptive process for improving said signal-to-noise plus interference ratio.

10. The method according to claim 9 further comprising selectively weighting and combining said at least one alternate sub-array output signal from a first one of said sub-arrays with a second alternate sub-array output signal from at least a second one of said sub-arrays in a fully adaptive process for producing an alternate array output signal having a second signal-to-noise plus interference ratio

11. The method according to claim 10 further comprising the step of estimating an angle-of-arrival direction for a second SOI and at least one said SNOI.

12. The method according to claim 11 further comprising the step of calculating a new set of weighting factors for controlling at least one said alternate sub-array beam to improve said second signal-to-noise plus interference ratio obtained for said SOI in said alternate array output signal.

13. The method according to claim 12 further comprising the step of selectively controlling said alternate weighting factors for said at least one alternate sub-array beam in accordance with said calculating step.

14. In a phased array antenna system having a plurality of antenna elements configured as a plurality of sub-arrays, a system for cascaded processing of signals to reduce interference from at least one undesired signal, comprising:

a plurality of sub-array processors for selectively applying a weighting factor to each of said antenna elements to form a plurality of sub-array beams, each pointed in a selected direction, and for combining an output from each said antenna element in said sub-arrays to produce a plurality of sub-array output signals;

at least one array processor for selectively weighting and combining said sub-array output signals received from at least a first one of said sub-arrays with a sub-array output signal from at least a second one of said sub-arrays in a fully adaptive process for producing an array output signal having a signal-to-noise plus interference ratio;

an array system processor for estimating an angle-of-arrival direction for a SOI and at least one SNOI and, calculating a new set of weighting factors based on said estimated angle-of-arrival direction information for controlling at least one said sub-array beam to improve said signal-to-noise plus interference ratio obtained for said SOI in said array output signal; and

control circuitry for selectively controlling said weighting factors for said at least one sub-array beam for applying said new set of weighting factors.

15. The system according to claim 14 wherein said controlling circuitry is responsive to array system processor for adjusting said weighting factors for at least one of said sub-arrays for re-pointing said sub-array beam.

16. The system according to claim 14 wherein said control circuitry is responsive to said array system processor for adjusting said weighting factors for at least one of said sub-arrays to produce a sub-array beam pattern comprising regions of relatively higher and lower gain to improve said signal-to-noise plus interference ratio.

17. The system according to claim 16 wherein said array system processor is configured for calculating a surrogate covariance matrix based solution for at least one of said sub-arrays.

18. The system according to claim 14 wherein said weighting factor is selected from the group consisting of exclusively amplitude, exclusively phase, time-delay and complex weights associated with each said antenna element.

19. The system according to claim 14 wherein said array system processor estimates an incident power for at least one of said SOI and said at least one SNOI.

20. The system according to claim 14 wherein said sub-array processor is responsive to said array-system-processor for initially pointing at least one said sub-array toward a region of angular space expected to contain said SOI.

21. The system according to claim 14 wherein said array system processor estimates an angle-of-arrival direction for said SOI and said at least one SNOI based on at least one of:

blind source separation (BSS) techniques;

a priori knowledge;

direction information of signals learned during system operation.

22. The system according to claim 14 wherein at least one said sub-array processor selectively applies at least one alternate weighting factor to each of said antenna elements in at least one of said sub-arrays to independently form at least one alternate sub-array beam using said antenna elements.

23. The system according to claim 22 wherein said at least one sub-array processor combines an output from each said antenna element produced using said alternate weighting factor to produce at least one alternate sub-array output signal.

24. The system according to claim 23 wherein said array processor selectively weights and combines at least one of said sub-array output signals with said at least one alternate sub-array output signal in a fully adaptive process for improving said signal-to-noise plus interference ratio.

25. The system according to claim 24 wherein said array processor selectively weights and combines said at least one alternate sub-array output signal from a first one of said sub-arrays with a second alternate sub-array output signal from at least a second one of said sub-arrays in a fully adaptive process for producing an alternate array output signal having a second signal-to-noise plus interference ratio

26. The system according to claim 25 wherein said array system processor further estimates an angle-of-arrival direction for a second SOI and at least one said SNOI.

27. The system according to claim 26 wherein said array system processor calculates a new set of weighting factors for controlling at least one said alternate sub-array beam to improve said second signal-to-noise plus interference ratio obtained for said SOI in said alternate array output signal.

28. The system according to claim 27 wherein said array system processor selectively controls said alternate weighting factors for said at least one alternate sub-array beam based on said new set of weighting factors.